IIJORT and SCHRECK: PHRNOTYI'IC DIFFFRFNC'KS AMONC COHO SALMON 



fish from tributaries of streams that had re- 

 ceived a large supplement of a normative hatch- 

 ery stock in the previous 6yr. This was to ensure 

 that characterization of the genotype would re- 

 flect environmental considerations rather than 

 introgression of foreign stocks. 



Morphological Characters 



For each sample, 15 carcasses were frozen for 

 later counts. Scales in the lateral series were 

 counted in the second row above the lateral line, 

 starting with the anteriormost scale and ter- 

 minating at the hypural plate. Scales above the 

 lateral line were counted from the anterior in- 

 sertion of the dorsal fin to the lateral line. Anal 

 ray counts did not include the short rudimentary 

 anterior rays, and branched rays were counted 

 as one. The total number of gill rakers on the first 

 gill arch was recorded. Alizarin red was used to 

 highlight rudimentary gill rakers. The total 

 number of branchiostegal rays from both sides 

 was counted. Vertebral counts, made on X-ray 

 plates, included the last three upturned centra. 

 Accuracy of morphological counts was checked 

 by recounting two fish from each sample. If 

 errors were found, additional fish from that 

 sample were recounted to correct for any error. 



Electrophoresis 



Blood and white muscle samples were col- 

 lected from the fish that were not used for 

 morphological counts. The caudal peduncle was 

 severed and the blood collected in heparin- 

 ized microhematocrit tubes that were then cen- 

 trifuged and stored at — 10°C. White muscle 

 samples (1 cm 3 ) were removed from the anterior 

 dorsal portion of the frozen carcasses, homo- 

 genized with 2 or 3 drops of water, and then cen- 

 trifuged to clear the supernatant. Only the 

 blood serum and supernatant were used for elec- 

 trophoresis. 



The methodology for electrophoresis of trans- 

 ferrin and phosphoglucose isomerase followed 

 the basic principles of May (1975) with some 

 modifications by Solazzi. 4 The gel and elctrode 

 buffers were described by Ridgway et al. (1970). 

 Four genotypes of transferrin (AA, AC, CC, and 

 BC) in the serum samples were interpreted ac- 



4 Solazzi, M. F. 1977. Methods manual for the electro- 

 phoretic analysis of steelhead trout (Salmo gairdneri). Oreg. 

 Dep. Fish Wildl., Res. Sect., Inf. Rep. Ser. Fish. 77-7, 35 p. 



cording to Utter et al. (1970). Transferrin was 

 recorded as the frequency of the "A" allele, since 

 the "B" allele was relatively rare. The variant 

 allele for the second locus of phosphoglucose 

 isomerase, first observed in white muscle tissue 

 by May (1975), was recorded as the frequency of 

 this variant allele. 



Life History 



The life history characters we used were time 

 of peak spawning and proportion of females in 

 the adult population. We estimated the peak 

 spawning times on the basis of interviews with 

 district fishery biologists and hatchery man- 

 agers. Whenever possible, we verified the esti- 

 mates with spawning ground survey records and 

 hatchery records. We stratified the peak spawn- 

 ing times into five segments of 2 wk each. 



The proportions of adult females (3 yr olds) 

 were estimated from hatchery records and 

 spawning ground surveys. This character is an 

 indirect measure of the proportion of jacks 

 (males that mature at 2 yr of age) in the popula- 

 tion. Populations with high proportions of jacks 

 in a given year should have relatively higher pro- 

 portions of females returning the next year. A 

 direct measure of the proportion of jacks cannot 

 be used because body size differences between 

 jacks and 3-yr-old adults affect the catch in gill 

 net fisheries, retention in hatchery holding 

 ponds, recovery of carcasses on spawning ground 

 surveys, and catch rate in sport fisheries. 



Environmental Data 



Stream characteristics include distance up- 

 stream to spawning grounds, basin area, area 

 and length of the estuary on the stream system, 

 latitude, gradient, spring runoff, the presence or 

 absence of the myxosporidan parasite, Cerata- 

 myxa shasta, and the presence or absence of the 

 following nine species of fish: carp, Cyprinus 

 carpio; Oregon chub, Hybopsis crameri; north- 

 ern squawfish, Ptycholcheilus oregonensis; 

 speckled dace, Rhinichthys osculus; redside 

 shiner, Richardsonius balteatus; largescale 

 sucker, Catostomus macrocheilus; brown bull- 

 head, Ictalurus nebulosus; largemouth bass, 

 Micropterus salmoides; and striped bass, Morone 

 saxatilis. To separate the populations that have 

 short and potentially long swimming distances 

 to the spawning grounds, we measured spawn- 

 ing distances from the mouth of the stream sys- 



107 



